Manufacture of tubes from polystyrene and the like substances



July 14, 1936. FISCHER 2,047,554

MANUFACTURE OF TUBES FROM POLYSTYRENE AND THE LIKE SUBSTANCES Filed Feb. 15, 1935 Patented July 14, 1936 UNITED STATES PATENT OFFICE MANUFACTURE OF TUBES FROM POLY- STYRENE AND THE LIKE SUBSTANCES Application February 15, 1935, Serial No. 6,637 In Germany February 13, 1934 1 Claim.

My invention relates to the manufacture of hollow shaped bodies from polystyrene and the like substances.

The manufacture of shaped bodies from 6 polystyrene, i. e., a material appertaining chemically to the group of the polyvinyl compounds presents great difiiculties in spite of the thermoplasticity thereof. As is well known polystyrene may be pressed as a matter of fact in a heated state into the desired shape as is possible in the case of the insulating press materials hitherto known. Also experiments have already been carried out to work polystyrene in a manner similar to the well-known metal spraying method for the production of shaped bodies. The shaped bodies thus manufactured present, however, the drawback that they are brittle and inflexible at normal temperatures, so that their possibility of use is considerably restricted.

It has already been proposed to render the shaped bodies of polystyrene less, brittle and more pliable by subjecting them during formation to a mechanical stress, 1. e., particularly by causing them to elongate during formation. In this manner it was actually possible to manufacture ribbons, filaments, section wires and the like of less brittleness and sufficient pliability so that they may be utilized for a variety of purposes.

However, no method has hitherto been known to continuously produce particularly thin-walled tubular bodies from polystyrene, since the methods hitherto employed in connection with the manufacture of shaped bodies of polystyrene 35 practically only ensure the production of solid bodies. My invention has for its object to provide a method, whereby hollow shaped bodies may be manufactured without losing the greater pliability aforementioned. The invention is shown in diagrammaticform in the accompanying drawing.

The method according to the present invention consists in shaping at a suitably increased temperature preformed and at least partially hollow bodies of polystyrene by means of compressed fluid, particularly in expanding the same and in giving them their final shape. Particularly compressed air may be employed as compressed fluid. The method is preferably carried out so that in forming the body of polystyrene its walls are also stretched at thesame time, which reduces the brittleness and increases the pliability of the material.

By way of explanation I may state that this stretching of polystyrene does not merely offers free passage for polarized light, while 5 when stretched to the extent at which it becomes flexible, for instance, to at least twice its original dimensions, the material becomes opaque to such light.

As shown in the drawing, and in accordance 1 with the novel method involved in the invention, a pre-shaped polystyrene tube, leaving the mouth of a tube press and still possessing a sufficiently high temperature may pass along a molding channel or a molding calibrator of appreciable length, with which it comes gradually into contact or against which it is gradually pressed. This form of the invention is shown in Fig. 2 in a diagrammatic form. The polystyrene tube l3 leaving the mouth ll of the tube 2 press I2 is filled with compressed air by means of the compressed air conduit-l4 ending in the mouth ll of the mold and passes for a short distance through the intermediate mold tube I5 having approximately the same inner diameter 2 as the mouth piece H and which, if desired, may be designed as cooling tube, so that at the end of the intermediate tube IS a temperature prevails required for shaping the body to the desired final form. The polystyrene tube l3 then en- 3 ters the final calibrating tube It which gradually increases in size, and in which the diameter of the polystyrene tube is increased to the final value by means of the compressed air introduced therein at the mouth H of the press l2. 3 If desired, a cooling tube I! may surround the calibrating tube IE to cool down the polystyrene tube, for instance, to the room temperature. The method may, if desired, be also carried out without the intermediate tube IS, the polystyrene tube I3 travelling in this case freely for a short distance, thus permitting it to expand to a slight extent by the compressed air prior to its introduction into the calibrating tube l6. Owing to the expansion of the polystyrene tube its walls become thinner so that the action of the compressed air on the tubular wall becomes stronger and stronger and is finally limited when the polystyrene tube enters the calibrating tube I6, whose diameter in this form of the 50 invention must be greater than the inner diameter of the mouth ll of the press l2. In both forms of the invention the polystyrene tube is pressed at a relatively short distance from the press uniformly against the inner wall of the calibrating tube by the compressed air and continuously subject to the compressed air. so that the tightness oi the tube to be formed may be easily checked up thereby. The tubes thus produced, after their complete cooling down, may be coiled into rings in any desired manner. To enhance the flexibility the walls of the polystyrene tube maybe advantageously corrugated or grooved, which may be either eflected bythe calibrating tube II or also by means of particular devices disposed behind the tube II. To facilitate the feed of the polystyrene tube special ieed devices may be employed, for instance, in the form or a caterpillar tractor, or lubricants may be employed which do not undergo a reaction with the polystyrene.

The method according to the invention is not limited to the use of polystyrene but may also be applicable to similar substances, particularly oi the polyvinyl group or other hydrocarbon groups.

I claim as my invention:

The method of continuously forming thinwalled pliable tubes of polystyrene or the like, consisting in extruding a tube of polystyrene 01 a diameter smaller and o! a wall thickness greater than the final tube into a preliminary mold of suitable temperature. introducing a compressed fluid into said smaller tube and gradually expanding said smaller tube by said -fluid into a mold of the ilnal tube size while the smaller tube advances during extrusion through the preliminary mold, whereby for a given final- 1y expanded tube size and wall thickness the relation between the diameter of the smaller tube and its wall thickness is chosen so that the material is suiiiciently stretched during expansion into final size, to diminish its brittleness.

ERNST FISCHER. 20 

